Aspergillus fumigatus is a clinically important fungal pathogen that causes invasive disease in immunocompromised hosts. Leukemia patients receiving intense chemotherapy regimens and bone marrow transplanted patients are particularly at risk for Invasive Aspergillosis (IA) with an associated mortality rate of approximately 90%. Studies in mouse models of IA have suggested that Aspergillus-specific IFN-gamma secreting T lymphocytes play a protective role by limiting invasive fungal disease while IL-4 and IL-13 producing T cells have a deleterious impact. Although it is clear from these studies that CD4 T cells influence the outcome of A. fumigatus infection, many of the factors that determine T cell activation and recruitment remain poorly defined. Moreover, it remains to be determined whether Aspergillus-specific CD4 T cells can mediate the resolution of established disease. In order to begin to address these questions, the candidate, Dr. Amariliz Rivera, cloned CD4 T cells specific for A. fumigatus, isolated the genes encoding the antigen specific alpha and beta chains of the T cell receptor (TCR) and generated TCR transgenic mice. Preliminary results demonstrate that these mice express a functional TCR that recognizes A. fumigatus hyphae. The availability of monoclonal Aspergillus-specific CD4 T cells will give the candidate the unique opportunity to address the following aims: 1) to characterize the activation and differentiation of CD4 T cell responses to inhaled A. fumigatus spores, 2) to establish the role of the regulatory cytokines IL-10 and TGFbeta in this process, 3) to examine the influence of concurrent innate inflammatory responses on T cell activation and 4) to establish whether A. fumigatus-specific T cells can confer protection from IA. Furthermore, these studies will establish the foundation for the potential therapeutic use of CD4 T cells against fungal infections in the cancer patient. Dr. Rivera will perform these studies under the guidance of Dr. Eric G. Pamer at Memorial Sloan Kettering Cancer Center. Through this K01 award the candidate will gain the skills and experience necessary to successfully compete for an independent faculty position. As a woman of Puerto Rican descent the candidate will strive to be an outstanding role model for younger Hispanic scientists.